During tumor development, benign neoplastic cells are influenced by the expression of cytokines, growth factors, and proteases present in the tumor microenvironment. Epidermal growth factor (EGF) is the most studied growth factor and is considered important for cell proliferation and migration. Metalloproteinases (MMPs) are also involved in tumor progression. The present study aimed to analyze the proliferation, viability and migration index of pleomorphic adenoma myoepithelial cells, in addition to the secretion of MMPs with EGF supplementation. Benign myoepithelial cells were cultured with two different EGF doses (5 and 10 ng/ml), and the influence of EGF on cell proliferation and viability, using trypan blue and MTT assays, respectively, after 24, 48, and 72 h, was evaluated. To analyze cellular morphology, hematoxylin-eosin staining and indirect immunofluorescence using the anti-vimentin antibody, was performed. In vitro migration assays were performed in Transwell chambers with an 8-μm pore covered with Matrigel and supplemented with 5 or 10 ng/ml of EGF, after 96 h. After 4 days of cell culture, ELISA was performed to determine the MMP-2 and MMP-13 levels. One-way analysis of variance (ANOVA) with post hoc Tukey test was applied, with a significance level of 0.05. The results revealed that EGF influences myoepithelial cell morphology, without alteration of proliferation and viability. The migration assay showed that EGF increased the mean index from 16 % in the control group to 40 and 76 % for 5 and 10 ng/ml of EGF, respectively. ELISA revealed that when the cells were supplemented with either of the EGF doses, an increase in MMP-2 levels was observed when compared with the control group (C). This study concludes that EGF aids in the production of MMP-2, which favors the dissolution of the basement membrane, contributing to cell migration and tumor progression, hence permitting contact between the myoepithelial cells and stroma.

Abstract. The aim of the present study was to analyze the in vitro effect of various doses of epidermal growth factor (EGF; 5 and 10 ng/ml) on matrix metalloproteinase-2 (MMP-2) secretion and E-cadherin/β-catenin expression by co-cultured cells that mimic an in situ carcinoma ex-pleomorphic adenoma, where benign myoepithelial cells from a pleomorphic adenoma surround malignant epithelial cells. EGF was supplemented in various doses and the effects were evaluated following four days of cell culture. ELISA was performed to determine MMP-2 secretion levels. Gene expression for E-cadherin and β-catenin was analyzed using quantitative polymerase chain reaction. The results revealed that E-cadherin expression decreased when the cells were supplemented with 5 ng/ml EGF. ELISA results indicated that MMP-2 secretion increased when EGF was supplemented at concentrations of 5 and 10 ng/ml. The present findings demonstrated that EGF may be involved in the epithelial-mesenchymal transition process via altering the E-cadherin/β-catenin complex and increasing MMP-2 secretion, which may then favor the dissolution of the basement membrane to the benefit of malignant cell clusters, contributing to the development of an invasive phenotype in this in vitro model of tumorigenesis.

Background There has been great interest recently in the mechanisms of cell‐to‐cell communication through microvesicles (MV). These structures are produced by many different cell types and can modulate cellular activity by induction of epigenetic alterations. These vesicles may promote tumor mass increase either by stimulating cell proliferation via growth factors or by inhibiting apoptosis, which reinforces the role of such vesicles as important modulators of tumor progression. Methods The present in vitro study aimed to characterize MV derived from malignant neoplastic epithelial cell cultures (EP) and their effect on the expression of apoptosis/autophagy and invasion related genes of benign myoepithelial (Myo) cell cultures. Results The results revealed round structures with a mean size of 153.6 (±0.2) nm, with typical MV morphology. CD63 quantification indicated that EP cell culture at 70%‐80% confluence secreted 3.088 × 108 MV/mL. Overall, Myo exposed to MVs derived from EP showed both up‐ and downregulation of tumorigenesis promoting genes. MVs from EP cells promoted cell death of Myo cells and positively modulate BAX, SURVIVIN, LC3B, MMP‐2, and MMP‐9 expression. Furthermore, an increasing of MMP‐2 and MMP‐9 secretion by Myo was observed after MV exposure. Conclusions These findings suggest that MVs from EP modulate autophagy of Myo cells, which may, in part, explain the disappearance of these cells in in situ areas of invasive carcinoma ex‐pleomorphic adenoma. Additionally, the overexpression of MMPs contributes to the development of an invasive phenotype of Myo cells, which could favor the dissolution of the basement membrane during tumorigenesis process.

Myoepithelial cells have been implicated in the regulation of the transition from in situ to invasive neoplasia in salivary gland tumors. Considering the importance of the microenvironment of the tumor, the present in vitro study therefore analyzed the morphological and phenotypic changes undergone by benign myoepithelial cells from pleomorphic adenoma (PA) stimulated by tumor-conditioned medium. The benign myoepithelial cells were obtained from PA and were cultured with fibronectin extracellular matrix protein, supplemented with tumor-conditioned medium, which was harvested from breast ductal adenocarcinoma AU-565 and melanoma Hs 852.T cells. The morphological alterations were assessed by immunofluorescence analysis using vimentin antibody. The α-smooth muscle actin (α-SMA) and fibroblast growth factor (FGF)-2 proteins were analyzed by indirect immunofluorescence and quantitative polymerase chain reaction (qPCR). No morphological changes were observed in the myoepithelial cells cultured in fibronectin protein under stimulation from either tumor-conditioned medium. The immunofluorescence results, which were supported by qPCR analysis, revealed that only α-SMA was upregulated in the fibronectin substratum, with or without tumor-conditioned medium obtained from breast ductal adenocarcinoma and melanoma cells. No significant difference in FGF-2 mRNA expression was detected when the cells were cultured either in the tumor-conditioned medium or in the fibronectin substratum. The tumor-conditioned medium harvested from breast ductal adenocarcinoma and melanoma did not affect myoepithelial cell differentiation and function, which was reflected by the fact that there was no observed increase in α-SMA and FGF-2 expression, respectively.

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